Question

The sum of a certain number of terms in an A.P. is 5500. The first and the last terms are 100 and 1000. Find the number of terms.

Answer 1

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Answer 2

Answer:

Number of terms = 10

Step-by-step explanation:

Given data

sum of a certain number of terms in a AP = 5500

               given first term $a$ = 100

                          last term $l$ = 1000

we know that sum of the n terms in a AP = $\frac{n}{2} (a +l)$  

here $a$ = first term = 100  

        $l$ = last term = 1000  

therefore,  5500 = $\frac{n}{2} (100 +1000)$  

                  5500 = $\frac{n}{2} (1100)$

                n(1100) = 2(5500)

                    n(11) = 2(55)

                        n = 2(5) = 10

Number of terms = 10